1. Field of the Invention
The disclosed embodiments relate to medical devices. More specifically, the disclosed embodiments relate to catheters that are inserted into blood vessels or the like.
2. Description of Related Art
A catheter that is inserted into a tubular organ, such as a blood vessel, an alimentary canal, or a ureter, or an internal bodily tissue, structurally includes an inner layer (base tube) made of a resin, an outer layer surrounding the outer periphery of the inner layer and made of a resin, and a braid (reinforcement layer) interposed between the inner layer and the outer layer. This braid is formed by weaving wires made of a metal such as copper or stainless steel together in consideration of properties required for a catheter, such as pushability, torque transfer capability, and pressure resistance (see Japanese Unexamined Patent Application Publication No. 2001-87389, for example).
If such a braid were to extend up to a distal end portion of a catheter, the distal end portion of the catheter would have no flexibility. In view of this, a catheter having a distal end portion that is made flexible by cutting part of the braid (see Japanese Unexamined Patent Application Publication No. 2011-72562, for example) has been developed. In addition, a catheter has been developed in which an area over which a distal tip made of a resin is bonded to a distal end portion of the catheter is increased by partially cutting off the distal end portion of the catheter such that the distal end portion of the catheter has a slope so that the distal tip and the distal end portion of the catheter may be highly reliably bonded together (see U.S. Pat. No. 5,509,910, for example).
In the above structure, however, since part of the braid in the distal end portion of the catheter is completely cut off, the intrinsic pushability or torque transfer capability of the catheter is reduced. In addition, even if the distal end portion of the catheter is obliquely cut, the distal tip is mainly bonded to only the outer layer due to the presence of the braid, thereby negligibly improving the tensile strength of the distal tip.
As illustrated in FIG. 7, since the distal end portion of an existing braid is cut by a laser beam or the like, the distal end portion has fine projections and depressions arranged in the circumferential direction of the catheter. When the catheter is pushed through an object, the distal end portion of the braid penetrates the distal tip in some cases because there are a large number of projections formed in the distal end portion of the braid. Particularly, in the case where a catheter required to be small for reducing a patient treatment burden has a distal tip having a small thickness or a short length, such a problem is more likely to occur.